feat: add tree_with_rewrites::Change(Ref)::previous_location()

That way, it's also possible to obtain the previous location in case of rewrites.

Author: Byron

gix-diff/src/tree_with_rewrites/change.rs

@@ -444,6 +444,17 @@ impl<'a> ChangeRef<'a> {
             | ChangeRef::Rewrite { location, .. } => location,
         }
     }
+
+    /// Return the *previous* location of the resource where possible, i.e. the source of a rename or copy, or the
+    /// location at which an addition, deletion or modification took place.
+    pub fn source_location(&self) -> &BStr {
+        match self {
+            ChangeRef::Addition { location, .. }
+            | ChangeRef::Deletion { location, .. }
+            | ChangeRef::Modification { location, .. } => location,
+            ChangeRef::Rewrite { source_location, .. } => source_location,
+        }
+    }
 }
 
 impl Change {
@@ -477,4 +488,15 @@ impl Change {
             | Change::Rewrite { location, .. } => location.as_bstr(),
         }
     }
+
+    /// Return the *previous* location of the resource where possible, i.e. the source of a rename or copy, or the
+    /// location at which an addition, deletion or modification took place.
+    pub fn source_location(&self) -> &BStr {
+        match self {
+            Change::Addition { location, .. }
+            | Change::Deletion { location, .. }
+            | Change::Modification { location, .. } => location.as_bstr(),
+            Change::Rewrite { source_location, .. } => source_location.as_bstr(),
+        }
+    }
 }